1. Field of the Invention
The present invention relates to a spread illuminating apparatus used as an illuminating means for signboards, various kinds of reflection-type displays, etc., and more particularly to a spread illuminating apparatus used as an illuminating means for a liquid crystal display.
2. Description of the Related Art
A demand for a liquid crystal display as a display mainly for computers has been increased since the liquid crystal display which operates on low power consumption is characterized by being thin and light weighted and so on. Since a liquid crystal which is a component member of the liquid crystal display does not emit light by itself, an illuminating means for viewing an image is required unlike a light emitting element such as a picture tube. In particular, in the recent demand for thinner devices, there has been a growing tendency to employ a spread illuminating apparatus of a side light type (light conductive member type) that is thin plate-like as an illuminating means for illuminating the liquid crystal display.
An example of such a side light type spread illuminating apparatus is shown in FIGS. 6 and 7.
In FIGS. 6 and 7, a spread illuminating apparatus 1 is, in general, constituted such that a bar-like light source 4 is disposed close to an end surface 3 of a transparent substrate 2 formed of a light-transmissible material. The transparent substrate 2 is formed in a wedge-shape, in which the thickness is in inverse proportion to the increase in the distance from the end surface 3 and gradually decreases.
The light source 4 is, in general, composed of alight conductive member 5 and a spot-like light source 6. The light conductive member 5 is made of a transparent material, formed in a long plate and disposed close to and along the end surface 3 of the transparent substrate 2, and the spot-like light source 6 is composed of an LED disposed facing one end 5a of the light conductive member 5. A reflection plate 7 is disposed facing the other end 5b of the light conductive member 5.
Further, a light reflection member 9, which is U-shaped, is disposed in such a manner as to cover longitudinal peripheral surfaces of the light conductive member 5 except a surface 5c (first surface of the light conductive member) facing the transparent substrate 2 [covered are a surface 5d (second surface of the light conductive member) opposite to the first surface 5c of light conductive member and two surfaces extending in the longitudinal direction and being orthogonal to and continuous with the second surface 5d of the light conductive member (one on the upper side in FIG. 6 is referred to as third surface 5e of the light conductive member and one on the lower side in FIG. 6 is referred to as fourth surface 5f of the light conductive member)] and a portion 8 (transparent substrate proximal portion) positioned toward the end surface 3 of the transparent substrate 2.
A double-faced adhesive tape 10 is placed between the transparent substrate proximal portion 8 and opposing plates 9a and 9b of the light reflection member 9, which oppose each other, so that the light reflection member 9 is fixed to the transparent substrate proximal portion 8.
A light reflection pattern 12 is formed on a surface 11 of the transparent substrate 2 (the upper side in FIG. 6, hereinafter referred to as upper surface), and thus the brightness is almost uniform everywhere on the transparent substrate 2 irrespective of the distance from the light conductive member 5.
In the spread illuminating apparatus, it is desired that the spot-like light source be disposed on an electric wiring board (not shown) together with other electronic components in order to make the apparatus compact.
However, according to the conventional art described with reference to FIGS. 6 and 7, a reflection-type liquid crystal display element or the like are disposed under the spread illuminating apparatus, so there necessarily exists a distance equal to the thickness of the liquid crystal display element or the like between the spread illuminating apparatus and the electric wiring board. Therefore, it is difficult to dispose the spot-like light source 6 composed of an LED on the electric wiring board (not shown) together with other electronic components (electronic components used for electronic equipment provided with the liquid crystal display element, not shown). Thus, separate wiring paths have to be provided. In the above-described conventional art, since the separate wiring paths are provided, the circuit structure is complicated, which hinders the apparatus from becoming compact.
The present invention has been made in view of the above, and an object of the present invention is therefore to provide a spread illuminating apparatus which is improved in terms of compactness.
According to a first aspect of the present invention, there is provided a spread illuminating apparatus having a bar-like light source disposed along and in the vicinity of an end surface of a transparent substrate made of a transparent material, characterized in that the light source is composed of a light conductive member which is made of a transparent material, formed bar-like and disposed close to and along at least one end surface of the transparent substrate, and a spot-like light source which is disposed at at least one end of the light conductive member, and that a light guiding member which can change the direction of light beams is provided between the end of the light conductive member and the spot-like light source.
According to a second aspect of the present invention, in the spread illuminating apparatus of the first aspect of the present invention, the light guiding member is formed integrally with the light conductive member 5.
According to a third aspect of the present invention, in the spread illuminating apparatus of the first aspect of the present invention, the light guiding member is formed separately from the light conductive member.
According to a fourth aspect of the present invention, in the spread illuminating apparatus of the third aspect of the present invention, the light guiding member is comprised of at least one optical fiber.
According to a fifth aspect of the present invention, in the spread illuminating apparatus of any one of the first to third aspects of the present invention, the light guiding member is provided with a means for increasing reflection which improves light reflectance.